Did you use cheat-engine? It's the only thing I can think of that could fuck up your savefile to this extent.
1) Try "verify the integrity of the game data" on the game config on steam.
2) If that doesn't solve it, try to open "brownse local files", then uninstall via steam, then manually remove whatever folder of SoD2 that steam didn't auto remove, under the steamapp folder.
3) Then I would even manually remove my save folder: "C:\users\yourusername\appdata\local\SoD2" delete this folder.
After all that clean-up, try to reinstall via steam. If this doesn't solve it, then I would nuke the PC... just joking, maybe...